The invention relates to a method for in situ forming of an unstable oil in water emulsion which serves as an excellent well servicing fluid, and further which assists in production of viscous hydrocarbon from a subterranean well.
Many hydrocarbon reserves are in the form of viscous crude hydrocarbons, for example having API gravity of less than 26, and having viscosity at ambient temperatures of greater than 1200 cP. These hydrocarbons can be produced and refined into valuable end products, but pose difficulties in various aspects of the production stage.
Such crude hydrocarbons, by their nature, are difficult to pump or otherwise extract from the subterranean well, and are further difficult to transport through surface equipment and the like for the desired upgrading or refining.
Further, when a well is positioned into a viscous crude hydrocarbon bearing formation wherein the crude is as described above, the viscous crude hydrocarbon accumulates in the well, and can make well servicing difficult.
Methods for addressing this problem include, among others, the down hole formation of an emulsion of the hydrocarbon in water to reduce viscosity and make the resulting emulsion easier to pump to the surface. However, materials used in forming such down hole emulsions tend to adversely impact upon the formation, for example by causing swelling of the formation, which results in reduction in flowability of the hydrocarbon through the formation.
It is clear that the need remains for improved methods for servicing viscous crude hydrocarbon producing wells, and for producing such viscous crude hydrocarbon.
It is therefore the primary object of the present invention to provide a method for in situ or down hole forming of an oil in water emulsion which does not adversely impact the formation.
Other objects and advantages of the present invention will appear hereinbelow.
In accordance with the present invention, the foregoing objects and advantages have been readily attained.
According to the invention, a method is provided for in situ forming of an unstable oil in water emulsion, which method comprises the steps of providing a mixture of an aqueous alkali salt solution and a surfactant; and pumping said mixture down a well containing a crude hydrocarbon having an API gravity of less than about 26 so as to provide an unstable emulsion in said well, said unstable emulsion having said hydrocarbon as a dispersed phase and said solution as a continuous phase and having a ratio by weight of said hydrocarbon to said solution of at least about 50:50.